https://www.feedipedia.org/node/665
The worms are harvested using several different methods. Organic material (grass, etc.) can be layed on the ground and the worms come out of the ground and lay under the organic material which can then be rotated and the worms can be collected. Soil that are rich in worms can be screened to separate the worms from the soil, if the clay content is not high. After the worms have been collected they can be dried by laying them out in the sun or by using an artificially drying system. The amount of soil contamination will be directly correlated to the meal's ash content. Heating the worms at 120°C for one hour was found to improve growth in rats and reduced bacterial count (Velazquez et al., 1986).